Techniques are already known for marking articles by transferring a pattern printed on the inside face of a sleeve of heat-shrink plastics material, said pattern being transferred by the sleeve being shrunk onto the article concerned. Nevertheless, it should be observed that the transferred pattern is text or graphics printed by means of a special ink suitable for making the transfer (e.g. a sublimable ink), and that once the printed pattern has been transferred onto the article, the sleeve is of no further use and is removed from the article.
The present invention stems from a different approach, seeking to devise a technique for marking articles by transfer from a sleeve of heat-shrink plastics material which is shrunk onto the article, but in which the shrunk sleeve does not constitute a useless temporary medium, but can perform other functions, for example a function of tamperproofing and/or constituting a certificate of origin.
Document WO-A-96/02 434 describes the use of a heat-shrink strip associated with a cover of a container for a pharmaceutical. On the inside, the strip has a transferable portion (e.g. carrying the word "opened") which remains on the edge of the cover on first removal of the strip. An adhesive that is reactivatable by heat is used for transferring the label.
Documents WO-A-93/19 445 and US-A-5 292 018 describe techniques very close to that of the preceding document, with a message portion (or bar code) being transferred when the sleeve is shrunk.
Mention can also be made of document EP-A-0 345 405 which describes a card carrying a piece or medallion to which access is barred by an adhesive film having a hologram stuck to the article: any attempt at opening has the effect of delaminating the hologram, thereby providing the looked-for security.
In addition, security envelopes of heat-shrink plastics material have been known for a long time, in particular for association with the necks of bottles, and designed to constitute a guarantee of tamperproofing for the consumer, guaranteeing that the product concerned has not been subjected to fraudulent substitution or has not been spoiled maliciously. The security envelope heat-shrunk onto the neck of the bottle thus serves as an indicator of tampering in the event of an attempt at forcibly tearing or removing said envelope.
Nevertheless, with that security envelope technique, removal of the envelope, e.g. by pulling on an associated tear strip, leaves no portion or trace of the envelope on the article. Consequently, the function of constituting a certificate of origin remains, in practice, rather limited.